The present invention relates to a new and improved construction of a can for housing and dispensing liquid or pasty masses under pressure.
Among the numerous cans for liquid or pasty materials, generally referred to as "aerosol cans", in more recent times one particular type of such can has found wide acceptance. Such type can comprises a flexible, compressible, sack-like or bag-like inner container which has its opening edge fixedly held at the opening edge of an outer container by means of a flanged portion of a valve plate carrying a dispensing valve, and additionally, at the floor of the outer container there is provided a propellent-infeed opening which is closed by a stopper. Upon opening the valve the inner container is compressed under the action of the pressure of the propellent and the therein contained material escapes through the valve.
These known aerosol cans are associated with a number of drawbacks, particularly as concerns the fabrication thereof. Thus, for example, in order to obtain an adequate seal and safety of the can which is under pressure it is necessary to employ extreme care during the closing of the propellent filling opening at the floor of the can. Further, the attachment of the valve plate carrying the valve with the edge of the outer container, and above all, the realization of an adequate seal is appreciably more difficult than in the case of cans without an inner container, since the clamped edge of the latter results in there being available appreciably less sealng surface and hence the closing operation must occur with greater precision. A drawback of such aerosol cans resides in the fact that the opening of the outer container must be markedly constricted. Thus, for the present day standardized outer containers none of the standardized valve plates (together with the valves) which are generally intended for cans without inner bags can be employed. Nor can such cans be so employed with standardized valve plates. Therefore, special constructions for either the outer container or for the valve plate are required.
There are already known to the art aerosol cans, for instance from U.S. Pat. No. 2,816,691, which do not have the previously discussed drawbacks, yet are however associated with other defects. With such cans the bag-shaped inner container is not attached at the edge of the outer container, rather at a part of the valve protruding into the interior of the container. Additionally, there is no propellent-filling opening in the floor of the can, rather the propellent is filled, prior to attachment of the valve plate at the outer container edge, through its opening. One of the notable drawbacks of this state-of-the-art aerosol can resides in the need to fill its inner container prior to insertion into the outer container, if the dispensing valve is not also simultaneously designed as a filling valve, which in many instances is not possible or at least disadvantageous and in any event results in relatively long filling times. In order that the inner container in its filled condition can be introduced into the outer container its diameter must not exceed the opening edge of the outer container. With the present day can shapes this, however, results in relatively small inner containers having, in relation to the outer container, uneconomical, small take-up capacity for the material which is to be filled. Additionally, the filling of the inner container outside of the outer container is rather cumbersome.